A VLOM Handpump for 80 Metres

摘要

IT IS WELL accepted that handpumps designed for use in remote locations in developing countries should satisfy the VLOM (Village Level Operation and Maintenance) criteria if the pump is to be sustainable. In general terms the sustainability of a pump depends on (a) ease of use and maintenance, (b) durability (including corrosion resistance) and (c) the cost and availability of spare parts. However, at present there are no clear guidelines which quantify these factors, so there tends to be debate amongst pump designers, manufacturers and users as to how 'VLOM' certain pumps are. The two former factors (the 'technical' aspects) tend to be less critical for shallow (less than 30 metres) installations. The loads on the pump are low, allowing the use of lightweight and corrosion resistant plastics such as uPVC and HDPE, and mechanisms can be kept simple and relatively inexpensive. In deeper installations, however, the technical challenges are generally greater. As the loads on the pump increase, the use of stronger, heavier, (and more expensive) materials becomes necessary. This in turn often leads to the need for heavy lifting gear (tripods, chain blocks, pulleys etc) for maintenance, as well as more complicated mechanisms in the pump design. Capital costs, and cost of spare parts all increase, adversely affecting sustainability. At present there are several alternative VLOM pumps for shallow installations, however there are very few available for installations deeper than 45 metres. The added difficulty of spare parts distribution and government restrictions on allowable pump types also means that introducing new pumps on to the market is very difficult. This paper presents a new pump arrangement which addresses most or all of these difficulties.